RebE> ben adam lechavero includes ben adam lamakom hence greater but that does not mean to neglect the latter.
While balance may be a good start, there are several reasons to do more in L’Chavero:
1) there is always room for error in L’Chavero: these mitzvos depend on the other person and you can always make a mistake evaluating another person. For example, you think $10 is good enough to pay a worker, but he might think that he deserves $20. You think that coming on time to a class is respectful, the Rav might be offended that you are not there 10 minutes before. You bring a present to your wife, and she thinks that you did not bring it last year … this is way more likely that your halav stam will have camel milk in it. So, being machmir will keep you from an actual aveira
2) in addition to a mitzva, you are helping an actual person. See Chafetz Chaim story on doing kiddush before piyutim for a hungry guest. And as RebE is saying, any mitzva L’Chavero includes L’makom, so it’s like 3x effect.
3) if you want to be machmir in learning, same thing – L’chavero involves more details and requires more knowledge, and changes with time and place, so makes sense to spend more time on it.